Retinoblastoma is a rare childhood cancer of the eye. It appears in infants or young children at a frequency of about one in every 15,000 births. In some cases, there is a family (familial) history of the disease. It is curable if detected early, but often requires surgical removal of the eye.

The genetic cause of retinoblastoma has been extensively studied. Normally, individuals have two good copies of the retinoblastoma gene (RB-1) on chromosome 13. This RB-1 gene carries the information for making a protein called pRB which regulates cell division. When pRB is absent or defective due to defective (mutated) copies of the gene, uncontrolled cell division occurs, and cancer results. These patients also have increased risk of developing other types of cancer because pRB appears to be involved in many types of cancer besides retinoblastoma.

Retinoblastoma develops in individuals in whom mutation (an abnormality) has occurred in both...